Tungsten-nickel-iron shaping members

ABSTRACT

This invention is directed to the use of tungsten base alloys containing about 1 to 12 weight percent nickel and about 0.5 to 8 weight percent iron for die casting dies, molds, cores and other metal shaping members.

Larsen Jan. 7, 1975 [75] Inventor: Earl l. Larsen, Indianapolis, Ind.

[73] Assignee: P. R. Mallory & Co., Inc.,

Indianapolis, Ind.

[22] Filed: Sept. 22, 1971 [21] Appl. No.: 182,886

Related U.S. Application Data [63] Continuation-impart of Ser. No.590,088, Oct. 27, I966, abandoned, and a continuation of Ser. No.855,712, Sept. 5, 1969, abandoned.

[52] U.S. Cl 29/182, 75/176,164/138 [51] Int. Cl. C22c H04 [58] Field ofSearch 29/182; 75/176; 164/138 [56] References Cited UNITED STATESPATENTS 3,307,982 3/1967 Milligan et a1 148/133 X 400 Lu :1: o E v 300 IU) m Lu 0 D 200 O a:

w o E 100 n: 3 an TUNGSTEN-NICKEL-IRON SHAPING MEMBERS FOREIGN PATENTSOR APPLICATIONS 760,113 10/1956 Great Britain 29/182 OTHER PUBLICATIONSHurd, D. T., New Factor in Copper Alloy Casting," Precision MetalMolding, 23(10): p. 3738, Oct. 1965, TS200I35.

Primary Examiner-Benjamin R. Padgett Assistant Examiner-R. E. SchaferAttorney, Agent, or FirmHoffmann Meyer & Hanson [57] ABSTRACT Thisinvention is directed to the use of tungsten base alloys containingabout 1 to 12 weight percent nickel and about 0.5 to 8 weight percentiron for die casting dies, molds, cores and other metal shaping members.

7 Claims, 3 Drawing Figures IS /o Nl9/o CO5% MO 0.6 /0 TI "0. l /oAl-BALANCE Fe 0.4% C-O.35% NIH-1.1% Si- 50% Cir-0.9% V-l.25% M0- BALANCEF8 CYCLES x 1000 TUNGSTEN-NICKEL-IRON SHAPING MEMBERS This applicationis a continuation-in-part of Application Ser. No. 590,088, filed Oct.27, 1966 and a continnation of application Ser. No. 855,712, filed Sept.5, 1969, both abandoned.

Prior to this invention, most of the materials used as die casting dies,molds, cores, core pins and other metal shaping members were made fromtool steel. A typical tool composition for such die casting moldscontains about 5 percent chromium, 0.4 percent carbon, and minor amountsof vanadium and molybdenum.

While such tool steel dies are fairly satisfactory for forming lowmelting point metals and alloys of zinc, magnesium, and aluminum, a diematerial that would have longer life, resist erosion better, resistspalling and cracking, and be easier to machine would be highlydesirable. When die casting the higher melting point metals and alloyssuch as copper, brasses, and bronzes, these undesirable characteristicsare even more pronounced. Thus while prior art tool steel dies may becapable of making many thousands of parts of castings from zinc oraluminum alloys before they must be replaced, this is not true withcopper or its alloys such as brasses or bronzes. Forexample, when diecasting a brass alloy containing approximately 60 percent copper-40percent zinc at a temperature of 1,750F, the tool steel may begin tocrack and spall after as few as 1,000 castings have been made. Suchspalling and cracking occurs when the die is subjected to thermalstresses created by the molten high temperature alloys being forced intothe die under high pressure; while erosion of the die is generallycaused by the washing action of such high temperature alloys.

It is, therefore, an object of the invention to provide die casting diesor molds, cores and other metal shaping members which have a long life.

It is another object of the invention to provide die casting dies,molds, cores, core pins and other metal shaping members which will beresistant to erosion when subjected to the washing action of moltenmetals and alloys, particularly non-ferrous metals and alloys such ascopper, brass or bronze, aluminum and aluminum alloys, zinc and zincalloys, magnesium and magnesium alloys.

Another object of the invention is to provide die casting dies, andother shaping members which will resist cracking or spalling whensubjected to the thermal stresses created by molten metals and alloysbeing forced into dies and molds under pressure.

Another object of the present invention is to provide shaping memberswhich have resistance to thermal shock.

Still another object of the invention is to provide shaping memberswhich have resistance to erosion.

Still another object of the invention is to provide shaping memberswhich are resistant to spalling.

Still another object of the invention is to provide shaping memberswhich are resistant to cracking.

Still another object of the invention is to provide shaping memberswhich have low surface roughness after continued operation.

It is another object of the present invention to provide shaping memberswhich require cleaning less frequently.

It is another object of the invention to provide shaping members havinggood mechanical properties both at room temperature and at elevatedtemperatures encountered in die casting operations.

Another object of the present invention is to provide shaping memberswhich rapidly remove heat from the metals and alloys being cast.

Another object of the present invention is to provide a method ofcasting resulting in increased life of casting components includingdies, molds, cores, core pins and other shaping members.

Another object of the present invention is to provide a method ofincreasing the life of casting components including dies, molds, cores,core pins and other shaping members.

Other objects will be apparent from the following description anddrawings.

In the drawings:

FIG. 1 is a cross section of an exemplary die casting die or mold;

FIG. 2 is a cross section of another exemplary die or mold; and

FIG. 3 is a graph comparing the surface roughness of dies made inaccordance with the present invention with various die materials of theprior art.

Generally speaking, the objects of the invention are accomplished byutilizing a die, mold, core or other metal shaping member having amolding surface com prising a tungsten-iron-nickel alloy. For example,the shaping members may comprise one or more die blocks defining aportion of a die cavity, as well as cores, core pins and other metalshaping members commonly associated with non-ferrous casting,particularly die castings, fabricated from an alloy comprising -99percent tungsten by weight, the balance being essentially iron andnickel, with said shaping member constituting at least a portion of thecasting cavity. The conduit or conduits, or other means to conductmolten metal to the casting cavity may also utilize surfaces made of atungsten-nickel-iron alloy, if desired.

Referring now to FIG. 1, an exemplary die casting die or mold 10 in themain comprises at least two blocks 11 and 12 each having a cavity 13 and14 the blocks being positioned adjacent each other to form a continu ousdie cavity 15 for forming a metal part. As shown, the casting die isheld within a block housing 16 com posed of two sections 17 and 18.Molten metal from which the part is to be formed, is fed to the cavity15, under pressure, by way of conduit 19. The shape of cavity 15 isdetermined by molding surfaces 13a and 14a. The shape of the cavity asshown in FIG. 1 is by way of illustration only, the particular shapebeing cast being dependent upon the shape of the part desired.

An important feature of the present invention lies in the material usedto fabricate the shaping members such as blocks 11 and 12 which definethe surfaces 13a and 14a. The present invention makes use of a tungstenbase alloy containing iron and nickel to give dies and other shapingmembers longer life even though high melting point metals and alloyssuch as copper, bronzes and brasses or other non-ferrous metals such asaluminum, aluminum alloys, zinc, zinc alloys, magnesium and magnesiumalloys are being molded. It is within the scope of the invention to formsuch surfaces from a tungsten-nickel-iron alloy coating upon the dieblocks, cores, core pins, or other shaping members.

Tungsten has little, if any, solubility in copper. This renders thematerial especially useful for the forming of parts from theafore-mentioned high melting point materials. However, pure tungsten haslow mechanical properties, is relatively brittle and is difficult tofabricate. Very high sintering temperatures are required, and to obtaina completely dense structure it usually is usually about 0.15 cgs unitsand preferably it is about 0.20 cgs units. The high thermal conductivityof the shaping members of the present invention tends to result insolid, sound casting; and the rapid rate of heat must be hot workedmechanically. 5 removal tends to reduce welding and erosion and ther- Onthe other hand, tungsten based alloys containing mal stresses. smallpercentages of iron and nickel can be formed by Another importantproperty of the shaping members powder metallurgy and liquid phasesintered at reasonof the present invention is that of the surfaceroughness able temperatures to make articles having densities of theshaping member cavity after prolonged use. In very near theoretical withhigh yield and tensile the case of steel shaping member cavities, thesurface strengths, good ductility, good impact strength, and roughnesshas been such that after as few as six to ten high resistance to thermalshock. Such alloys are thousand cycles of casting shots the cavitiesmust be readily machined utilizing ordinary machine shop tools polishedand/or machined because the surface has beand practices so thatintricate cavity shapes can be come too rough, resulting in castingdefects such as readily formed. And tungsten-iron-nickel alloys are poorsurface quality and/or cracking. This, usually insusceptible to heattreatment which increases not only volves shutting down the operationand/or down time, their tensile properties, but more important forcasting etc A surface roughness above ut 300 X 10 applications, theirductility. inches or higher is often considered to be too rough.

The shaping members of the present invention should By rthe shaping be so the present incontain from about 85 to about 99 weight percenttungvention can withstand many more cycles of operation sten, from about1 to about 12 percent nickel and from before such polishing and/ormachining is necessary. about 0.5 to about 7.5 percent iron. The ratioof nickel The cavity of the shaping members of the present into iron inthe shaping members of the present invention vention almost always havea surface roughness below should b f b t 1 t 1 t about 4 t 1, about 300X 10 inches after 50,000 cycles. It is usu- The p f d range f th h imembers f th ally below 300 X 10 inches after 70,000 cycles and presentinvention is from about 90 to about 98 weight y Often below 300 X 10*;inches after 80,000 y percent tungsten, from about 1.5 to about 8percent In fact, in a y instances the Surfacfi roughness is nickel andfrom about 0.5 to about 5 percent iron. Prefbelow 200 X after 50,000cycles, and even below erably, the ratio of nickel to iron is from about1.5 to 200 X inches after 701000 or 80,000 cycles- 1 to about 3 to 1With particular reference to FIG. 2, an exemplary ap- Th h i members f hpresent invention gemplication of the present invention is described. InFICi. ally have a tensile strength of at least 120,000 psi at afllecastmg (he or mold 2015 formed P l mom temperature d a i l Strength f atleast sections or blocks 21 and 22, the blocks being fabri- 75 000 i atroom temperature Elongation is imPorcated from an alloy consistingessentially of 95 percent tant because the shaping members mustwithstand ther- 92 percenfi nickel and Percent "'9" by mal shock. Theelongation is usually at least 3 percent Yvelghti blocks fi formed y qPhase ffor this reason and is often at least 5 percent (inches in g- Tdle held Wlthm a housmg 23 that 15 2 inches). Through heat treatingelongations of from 7 prmclpany made P of two Sections 24 and 25 and to25 percent .can be achieved and elongations in this backlng P 36 andrange are the most preferred for applications requiring Each 9 of thecontains a cavity and 29 particularly high resistance to thermal Shock 1each having a mold surface 20 and 31 the cavities being The preferredmethod of heat treatment comprises machined into the blocks. Cavities 28and 29 together heating the sintered compact to a temperature of withthe space 32 formed by the spaced relationship of 5000 12000C in aneutral or slightly reducing atm0 the blocks 21 and 22 form'thecontinuous die cavity 3 3. sphere for about one-half to 12 hours andthen quenchh Partlcular part belng formed s P m ing rapidly thisinstance comprises a tube having a /a inch I.D. and

. 1 Tensile strength at elevated temperature is very ima mch a length onInches" It has a A mch portant for the Shaping members of the presentinven thick collar X 2 inch 0.1). at one end. The molten metal tion. Ithas been found that in short time tensile tests form the tube fed to thecavlty through uall be obtained g i l gz gifig gg igzg g fiz z z Afterforming blocks 21 and 22 with their cavities,

SHORT TIME TENSILE STRENGTHS Composition Temp (Fl Tensile Strengths(psi) W, 7 Ni, 3Fe W, 3.5Ni, 1.5Fe

1200F 65,000 psi 70,000 psi 72,000 si 1500F 40,000 psi 45,000 psi 47,000psi I800F 20,000 psi 27,000 si 30,000 psi 2000F 15,000 psi 19,000 psi20,000 psi the blocks were heat treated to increase their ductility suchthat an elongation of about 15 percent was achieved. While not shown inFIG. 2, another die casting die identical in structure to that shown butconstructed of tool steel is positioned in the split block housings 24and 25 such that comparative results could The material used for castingwas 60 percent cop-' per-40 percent zinc alloy by weight. Thetemperature of the dies was maintained at about 500F by means of a gasheater. The temperature of the molten brass alloy was l,'750F. The alloywas injected into the die cavities at a pressure of about 18,000 psi.

After each stroke of the die casting machine in which a casting was madein each of the different dies, the cavities were cleaned of chips,flakes or flash remaining from the casting operation. This was done withan air blast which contained an oil, graphite, or other hydrocarboncompound. This left a carbonaceous film on the die cavities whichassisted in releasing the brass casting from the dies. After eighthours, it was necessary to remove the tool steel die to clear away thehard carbon base film that had built up in the cavity. The same type offilm built up or formed very slowly on the tungsteniron-nickel alloycavity and required cleaning only after 80 to 100 hours of operation.Thus there was much less down time and loss of production with thetungsteniron-nickel die.

Under these conditions, the tool steel dies had an average life on theorder of 5,000 castings. At this point they cracked and abraded to suchan extent that the castings could not be ejected. The cavity surfaceroughness was above 300 X inches. An examination of thetungsten-iron-nickel dies after they had produced 13,500 castingsrevealed them to be essentially the same as when they had been put intooperation (well below 200 X 10 inches). In fact, the die continued inoperation until after about 56,000 cycles when the test was stopped, butat which time the surface roughness was below 200 X 10' inches.

With reference to FIG. 3, there is shown a graph showing therelationship of the cavities surface roughness as it varies with thenumber of castings made for the types of tool steels tested and thetungsten-ironnickel die. Note the relatively little tendency for thesurface roughness of the tungsten-nickel-iron die to increase.

What is claimed is:

l. A shaping surface for shaping a molten high melting point material,the surface consisting essentially of about I to about 12 wt. percentNi, about 0.5 to about 7.5 wt. percent Fe, the ratio of Ni to Fe beingfrom about 1:1 to about 4:1, and about to about 99 wt. percent W, theshaping surface having a short time elevated temperature strength atabout 1,800 of at least about 20,000 psi and at about l,500F of at leastabout 40,000 psi, a thermal conductivity of at least about 0.15 cgsunits, an elongation of at least about 3 percent, and having a surfaceroughness of not more than about 300 X 10 inches after 50,000 cycles ofshaping molten high melting point materials.

2. The shaping surface of claim 1, wherein the shaping surface consistsessentially of about 1.5 to about 8 wt.% Ni, about 0.5 to about 5 wt.%Fe, the ratio of Ni to Fe is from about 1.511 to about 3:1, and about to98 wt. percent W, the thermal conductivity of the shaping surface is atleast 0.2 cgs units.

3. The shaping surface of claim 2, wherein the shaping surface consistsessentially of about 7 wt.% Ni, about 3 wt.% Fe, the balance W.

4. The shaping surface of claim 2, wherein the shaping surface consistsessentially of about 3.5 wt.% Ni, about 1.5 wt.% Fe, the balance W.

5. The shaping surface of claim 1, wherein the shaping surface isselected from the group consisting of a mold surface, a die surface, acore pin surface, and a core surface.

6. In a method of shaping a molten high melting point material includingthe steps of contacting the molten material with the shaping surface ofclaim 1 to shape the molten material, cooling the molten shaped material to solidify the material, and removing the solidified shapedmaterial from contact with the shaping surface.

7. In the method of claim 6, wherein the material to be shaped isselected from the group consisting of Cu, bronze, brass, Cu basematerials, Al, A] base materials,

Zn, Zn base materials, Mg, and Mg base materials.

1. A SHAPING SURFACE FOR SHAPING A MOLTEN HIGH MELTING POINT MATERIAL,THE SURFACE CONSISTING ESSENTIALLY OF ABOUT 1 TO ABOUT 12 WT PERCENT NI,TO ABOUT 0.5 TO ABOUT 7.5 WT. PERCENT FE, THE RATIO OF NI TO FE BEINGFROM ABOUT 1:1 TO ABOUT 4:1 AND ABOUT 85 TO ABOUT 99 WT. PERCENT W. THESHAPING SURFACE HAVING A SHORT TIME ELEVATED TEMPETATURE STRENGHT ATABOUT 1,800* OF AT LEAST ABOUT 20,000 PSI AND AT ABOUT 1,500*F OF ATLEAST ABOUT 40,000 PSI, A THERMAL CONDUCTIVITY OF AT LEAST ABOUT 0.15CGS UNITS, AN ELONGATION OF AT LEAST ABOUT 3 PERCENT, AND HAVING ASURFACE ROUGHNESS OF NOT MORE THAN ABOUT 300 X 10**-6 INCHES AFTER50,000 CYCLES OF SHAPING MOLTEN HIGH MELTING POINT MATERIALS.
 2. Theshaping surface of claim 1, wherein the shaping surface consistsessentially of about 1.5 to about 8 wt.% Ni, about 0.5 to about 5 wt.%Fe, the ratio of Ni to Fe is from about 1.5:1 to about 3:1, and about 90to 98 wt. percent W, the thermal conductivity of the shaping surface isat least 0.2 cgs units.
 3. The shaping surface of claim 2, wherein theshaping surface consists essentially of about 7 wt.% Ni, about 3 wt.%Fe, the balance W.
 4. The shaping surface of claim 2, wherein theshaping surface consists essentially of about 3.5 wt.% Ni, about 1.5wt.% Fe, the balance W.
 5. The shaping surface of claim 1, wherein theshaping surface is selected from the group consisting of a mold surface,a die surface, a core pin surface, and a core surface.
 6. In a method ofshaping a molten high melting point material including the steps ofcontacting the molten material with the shaping surface of claim 1 toshape the molten material, cooling the molten shaped material tosolidify the material, and removing the solidified shaped material fromcontact with the shaping surface.
 7. In the method of claim 6, whereinthe material to be shaped is selected from the group consisting of Cu,bronze, brass, Cu base materials, Al, Al base materials, Zn, Zn basematerials, Mg, and Mg base materials.